1. Field of the Invention
This invention relates to fuel handling, and, more particularly, relates to an improved type of cap for use on a gas can. Specifically, the invention relates to a self-venting gas cap which indicates whether the tank contains fuel for a two- or four-stroke engine, and which also provides an always-available, specially calibrated, measuring vessel for properly preparing a given oil and fuel mixture.
2. Description of the Prior Art
In the past, internal combustion engines have been widely used for diverse purposes. A typical application was the development of the outboard motor to propel boat. A fuel tank was a necessary companion to such an engine. The fuel tank for an outboard motor was typically a portable metal container, painted red for safety purposes. Other engine-driven equipment used similar fuel tanks.
Four-stroke engines used straight gasoline as fuel. Two-stroke engines used a gasoline and oil mixture as fuel. While oil-injection systems were developed for two-stroke engines, many two-stroke engines required that the oil be manually added to the gasoline. In a two-stroke engine, the fuel/air mixture circulates through the crankcase, and the oil component in the fuel mixture provides the necessary lubrication for the engine.
Since virtually all "gas cans" were painted red, it was difficult to tell whether a particular tank contained fuel for a two-stroke or a four-stroke engine. Since the added oil was essential to the proper operation of a two-stroke engine, it was critical to keep track of which of a group of fuel containers actually contained the oil. While one could remove the cap of the tank and manually investigate to determine which type of fuel the tank contained, the determination was difficult and the entire approach was inconvenient. In addition, the unnecessary removal of the gas cap was possibly dangerous.
The consequences of a fuel mix-up could be severe; if a two-stroke engine, which requires a gasoline-oil mixture for fuel, was instead operated on straight gasoline, bearing failure often followed.
A need continued to exist for an apparatus or method to provide a safe, apparent indication of the type of fuel in the tank.
In the case an outboard motor propelled by a two-stroke engine, it was typically necessary to manually measure the appropriate quantity of oil to be added. Since proper operation demanded that the quantity of oil added be quite precise, it was normally necessary to have a measuring device at hand when preparing a two-stroke fuel mixture. Unfortunately, it was often difficult to keep track of a separate measuring cup or device. Lack of an accurate measuring receptacle often resulted in use of a makeshift receptacle or an "eyeball" measurement. In any case, the cup or device was typically dirty when located. Thus, it was normally necessary to first clean the measuring device in order to avoid contaminating the mixture under preparation.
A need existed for a convenient, always-available, self-cleaning measuring receptacle for use in the preparation of a fuel mixture for a two-stroke engine.